Anoxic granular activated sludge process for simultaneous removal of hazardous perchlorate and nitrate

An airtight, anoxic bubble-column sequencing batch reactor (SBR) was developed for the rapid cultivation of perchlorate (ClO4-) and nitrate (NO3-) reducing granular sludge (GS) in this study. Feast/famine conditions and shear force selection pressures in tandem with a short settling time (2-min) as a hydraulic section pressure resulted in the accelerated formation of anoxic granular activated sludge (AxGS). ClO4- and NO3- were efficiently (>99.9%) reduced over long-term (>500-d) steady-state operation. Specific NO3- reduction, ClO4- reduction, chloride production, and non-purgeable dissolved organic carbon (DOC) oxidation rates of 5.77 ± 0.54 mg NO3--N/g VSS·h, 8.13 ± 0.74 mg ClO4-/g VSS·h, 2.40 ± 0.40 mg Cl-/g VSS·h, and 16.0 ± 0.06 mg DOC/g VSS·h were recorded within the reactor under steady-state conditions, respectively. The AxGS biomass cultivated in this study exhibited faster specific ClO4- reduction, NO3- reduction, and DOC oxidation rates than flocculated biomass cultivated under similar conditions and AxGS biomass operated in an up-flow anaerobic sludge blank (UASB) bioreactor receiving the same influent loading. EPS peptide identification revealed a suite of extracellular catabolic enzymes. Dechloromonas species were present in high abundance throughout the entirety of this study. This is one of the initial studies on anoxic granulation to simultaneously treat hazardous chemicals and adds to the science of the granular activated sludge process.